The present invention relates to the control of fuel gas flow to a burner and particularly to techniques for remotely varying the amount of fuel flow for maintaining the burner flame at a desired amount or level. The invention relates particularly to techniques for electrically remotely controlling the flow of gaseous fuel to a burner and more specifically to remote control of an electrically operated valve for modulating gas flow to the burner.
Heretofore, electrically operated valves employed for controlling flow fuel gas to a burner have been of the type having two states: either fully closed or fully open; and, the heat output of the burner is thus controlled by the percentage of the time during which the valve was fully opened. In fuel burners for furnaces and boilers utilized in heating buildings, typically the electrically operated burner valve is controlled by a thermostat which senses ambient temperature in the building and cycles the valve and burner ignition system accordingly.
It has been desired to provide for remote control of an electrically operated fuel gas valve in a cooking appliance in which heretofore the fuel gas valve has been either modulated manually by the user for surface burner control; or, an on/off electrically operated valve has been employed for the oven burner of the cooking appliance.
The competitiveness of the market for mass produced household cooking appliances requires that the cost of the burner and oven controls be minimized in order to facilitate manufacture and sale of the appliance. It has thus particularly been desired to provide a remotely controlled or modulating gas burner valve which enables such operation of a household range or oven in a manner which permits the range or oven to be sold competitively with cooking appliances which employ all-electric heating. Heretofore, all-electric appliances have provided on a cost competitive basis in the household cooking appliance market the ability to remotely or automatically control the level of heat by controlling the current flow in the electrical resistance heating elements in the top burner or oven easily and competitively by electrical or electronic means.
It has thus been long desired to provide a simple and reliable electrically operated modulating valve for a fuel gas burner which is reliable and sufficiently low in manufacturing costs to enable the burner control system to compete in the marketplace with all-electric heating element control systems.